Foam assessment

ABSTRACT

There are described methods and apparatus for assessing foams generated from liquids. Existing methods are slow and labor intensive. The new methods involve generating foams from liquids and optically obtaining information to enable parameters relating to the generated foam to be measured. Although single samples of liquids may be processed the methods are particularly suited to processing multiple samples to obtain data relating to foams at a high rate. The apparatus includes automated handling equipment to enable samples to be moved between workstations and relative to associated optical equipment that is used to obtain information relating to the foams.

CROSS REFERENCE TO RELATED APPLICATION

This application is the National Phase application of InternationalApplication No. PCT/GB2004/000711, filed Feb. 24, 2004, which designatesthe United States and was published in English. This application, in itsentirety, is incorporated herein by reference.

The invention relates to the measurement and assessment of foams.

Foam generation from liquids is a phenomenon that attracts significantattention. For example, the generation of good quality foam, asperceived by users, from personal care products such as shampoos andother cleansing formulations may add significantly to the commercialvalue of such products. Beverages, eg beers, cola drinks, cappuccinocoffee, is another consumer-oriented area in which foams, possiblytransient foams, are important in the perception of quality. In otherareas such as lubricants and engineering fluids, foams may bedetrimental to the performance of such fluids; alternatively, for someapplications, it may be advantageous to generate foams in such fluids.

In some applications, it may be sufficient to discriminate betweenliquids that generate foams by categorising them as high, medium or lowfoam-generating liquids. Such an assessment can be achieved forlubricants by using ASTM D892-95, which method measures foam height atpredetermined intervals and temperatures. Whilst providing gooddiscrimination between foams, this method is labour intensive,relatively slow and costly to carry out.

The effect of surfactants in base liquids may also be assessed usingASTM D 1173-53 (Re-approved 1997). However, again this method is labourintensive, relatively slow and costly to carry out.

The quality of foams may also be determined at least in part by the sizeand density of bubbles forming the foam. Smaller, more dense, ie greaternumber, bubbles tend to mean the foam has greater stability, iepersistence, and, in shampoos etc, better feel and similarcustomer-oriented properties. Conversely, large, less dense, bubblestend to be more transient which again, in customer-oriented productareas, may be part of the commercial value of the products.

In the personal care area, expert panels do such assessmentssubjectively. Such panels consist of people trained to generate foamsand make an assessment of parameters such as foam “whiteness”(assessment of bubble size), bubble size distribution, prevalence oflarge bubbles etc. Clearly, such methods are labour intensive, slow andcostly and do not necessarily provide consistent results.

There is, however, a significant problem in assessing the foamingcapability of formulations, whether containing foam-generating materialssuch as surfactants or foam-suppressing materials such as silicon-basedmaterials, on a consistent basis.

Owing to commercial pressures to produce better, more cost-effectiveformulations, high throughput screening (HTS) is being developed fromits origins in pharmaceutical and biotechnology applications to everydayproducts to enable the screening of large numbers of materials togenerate data banks from which new products can be identified andgenerated. Clearly, the methods described above are not suitable forrelatively high speed screening of large numbers of formulations usingHTS techniques.

Some attempts have been made to give a more quantitative analysis offoams: A Fains et. al., “Stability and Texture of Protein Foams: A Studyby Video Image Analysis” Food Hydrocolloids 11(1) 63-69 (1997); H HFiori et. al. “Computerised Image Analysis of Bubbles in GastricAspirate for Prediction of Respiratory Distress Syndrome” Acta Paediatr.90, 1402-1404 (2001); R Sanchez-Vioque et. al. “Foaming Properties ofAcylated Rapeseed Hydrolysates” J. Colloid Interface Sci. 244, 386-393(2001); and N J Hepworth, J Varley & A Hind “Characterising Gas BubbleDispersions in Beer”, Inst. Chem. Engineers Trans. IchemE 79,13-2-(March 2001). However, the techniques described in those referencesagain do not enable the relatively high speed screening of large numbersof formulations.

It is an object of the present invention to provide a method ofassessing foam that is consistent across samples and is reasonably fast.

It is another object of the present invention to provide a method ofassessing foam that is consistent across samples and is reasonably fastand is capable of being adapted as a high throughput screen to assessfoams.

According to a first aspect of the present invention, a method ofassessing foam generation from a liquid comprises:

-   -   a) introducing a measured quantity of the liquid into a tube;    -   b) after a predetermined period, generating a gas flow of        predetermined flow rate into said liquid to generate a foam from        the liquid in the tube;    -   c) using an opto-electronic device that is capable of generating        data relating to foam in the tube to obtain data relating to the        foam generated in the tube; and    -   d) using the data to assess the foaming ability of the liquid.

In one form of the method according to the first aspect of theinvention, the gas is passed through the liquid for a predeterminedperiod unless data from the opto-electronic device indicates thepresence of the top of the foam being generated before said periodexpires. This enables a simple high foaming/not high foaming assessmentto be made of liquids under test based on whether the top of the foambeing generated is detected in less than the predetermined gas flowperiod. Provided liquids generate sufficient foam to be detected by theopto-electronic device in less than the predetermined period, somedifferentiation of liquid foaming ability of the liquids may be possiblebased on time taken to foam detection.

In an alternative form of the method according to the first aspect ofthe invention, the height of the foam generated is detected to enable aquantitative assessment to be made of the foaming ability of the liquid.In this form of the method, the gas is passed through the liquid for apredetermined period unless data from the opto-electronic deviceindicates the presence of the top of the foam being generated beforesaid period expires. If data from the opto-electronic device indicatesthe presence of the top of the foam being generated before the expiry ofthe predetermined period, the foam is classed as having high foamingability; if data is not generated by the device, ie the top of the foamis not detected, before said period expires, on expiry of said periodthe gas flow is stopped and relative movement of the tube and theopto-electronic device with respect to one another enables the height ofthe foam generated in said period to be measured. Preferably, theopto-electronic device is moved relative to the tube. Preferably, theoptoelectronic device generates data relating to the positions of theair/foam and the foam liquid interfaces, the difference between thepositions being the height of the foam generated from the liquid in saidperiod.

Thus, liquids can be assessed as to whether they have a high foamingability or qualitatively have a foaming ability less than high, egmedium or low, depending on the height of foam measured.

Thus, the method according to the first aspect of the invention enablesa rapid and simple assessment of the ability of a liquid to generatefoam and to screen high numbers of such liquids for that ability.

Clearly, as discussed earlier, it would be advantageous to assessliquids not only on their ability to generate foam but also on thequality of the foam produced. This may be particularly important whenseeking to differentiate between a number of liquids that have similarfoam-generation ability.

According to a second aspect of the present invention, a method ofassessing the quality generated from a liquid comprises:

-   a) introducing a measured quantity of liquid into a tube;-   b) after a first predetermined period, generating a gas of    predetermined flow rate into the liquid to generate a foam from the    liquid in the tube;-   c) after a second predetermined period, stopping the gas flow and    measuring the height of the foam generated in the tube;-   d) in response to the height data generated in step c), positioning    an opto-electrical device at a location externally of the tube by    relative movement of the tube and the optoelectronic device with    respect to one another, the device being capable of capturing an    image of the foam;-   e) capturing an image of the foam; and-   f) analysing the captured image for parameters relevant to foam    quality.

Preferably, the height of the foam generated in the tube is determinedusing a second optoelectronic device capable of generating data relatingto foam in the tube. In one form of the method according to the secondaspect of the invention, relative movement of the tube and the secondopto-electronic device with respect to one another enables the height ofthe foam generated in said period to be determined. Preferably, the tubeis moved relative to the second opto-electronic device. Preferably, thesecond opto-electronic device generates data relating to the positionsof the air/foam and the foam/liquid interfaces, the difference betweenthe positions being the height of the foam generated from the liquid insaid period.

In a preferred form of the method according to the second aspect of theinvention, the second opto-electronic device is fixed relative to thetube position and captures an image of the whole foam head that isanalysed to provide a measurement of foam height.

The first opto-electrical device is positioned at a location externallyof the tube by relative movement of the tube and the firstopto-electronic device with respect to one another. In one form of thethe method according to the second aspect of the invention, relativemovement of the first opto-electronic device and the tube and withrespect to one another is achieved by moving the first opto-electronicdevice relative to the tube.

Although the location externally of the tube at which the firstopto-electrical device is positioned may be anywhere relative to thefoam volume that may be of interest, a convenient location isapproximately half the measured height of the foam. For many liquids,such a position is both remote from the liquid/foam interface, at whichbubbles tend to be very uniform, and remote from the foam/air interface,at which the foam is too aged and is deteriorating.

In a preferred form of the method according to the second aspect of theinvention, relative movement of the first opto-electronic device and thetube and with respect to one another is achieved by moving the tuberelative to first opto-electronic device.

The image captured by the first opto-electronic device is subjected toanalysis by suitable software, for example the KS300 Image AnalysisSystem available from Carl Zeiss Vision GmbH, Hallbergmoos, Germany. Thesoftware is configured to analyse the image for information of interest.

Thus, according to a third aspect of the present invention, a method ofanalysing an image of foam generated from a liquid comprises subjectinga digital, black and white image (image 1) of the foam to the followingoperations:

-   a) subjecting image 1 to a watershed segmentation process to produce    an image (image 2) in a graphics plane associated with the    electronic frame, image 2 being a line representation of bubble    walls of the foam;-   b) clearing image 1 from the image plane of the frame and merging    the graphics plane with the image plane of the frame to create a    binary image (image 3) consisting of lines representing the bubble    walls and a contrasting background and clearing image 2 from the    graphics plane; and-   c) measuring the dimensions of the bubbles in the image.

It will be appreciated that, in the binary image 3, the lines may beblack or white and the contrasting background white or black,respectively. However, in a preferred embodiment, in step b), in image 3the lines are white and the background, the bubble voids, is black.Preferably, before step c), image 3 is inverted to create an image 4 inwhich the bubble walls are black and the bubbles are white, image 4being the image used in step c).

Image 1 may be obtained as a black and white image or as a colour imagewhich is processed to be a black and white image. The colour image maybe processed by selecting at least one information channel (red, greenor blue) of the digital image and creating therefrom the black and whiteimage 1 in an electronic frame.

The method according to the third aspect of the invention may includesubsidiary steps to improve the quality of the images being processed.For example, if the lighting used during capture of the image of thefoam results in a shading across the image, image 1 is subjected to asmoothing operation, eg using a lowpass filter, to create a smoothedimage (image 1 a) followed by a shade correction process using image 1 ato produce an image (image 1 b) corrected for shading differences. It isthen image 1 b that is subjected to the watershed segmentation processin step b) of the preceding paragraph.

Other processes include erode and open operations to clean up theboundaries of the bubbles and to improve the differentiation of thespacing between the bubbles, ie the bubble walls. It is also possible toreduce or eliminate errors resulting from images of bubbles visiblethrough larger bubbles at the front of the image. That is achieved bysubjecting image 1, or image 1 b as the case may be, to an adaptivesegmentation process to produce a binary image (image 5) (the adaptivesegmentation is done “locally” in the image not globally). The purposeof this step is specifically to produce a binary image of the bigbubbles alone to enable features arising from bubbles behind, in theimage, the big bubbles to be minimised. This is achieved by setting thesize parameter and the threshold parameter (the big bubbles tend to alsobe lighter) for the adaptive segmentation process before carrying itout. The image 5 essentially contains images of just the big bubbles (orthe main parts of them). That image is then subjected to a scrapoperation to remove small white features within the black areas and afill operation to fill in holes in the white objects so they are morecomplete (image 6).

To further improve the quality of the data obtained, image 4 may beinverted so that it shows white lines and black blobs. Some of thesewhite lines are incorrect since they are from subsurface bubbles. Theinverted image 4 and image 6 are then subjected to a Boolean “SUBTRACT”operation to generate an enhanced image 4 on which, following an invertoperation, and optionally other operations such as thin, prune, dilateand open operations, the measurements are made. The Boolean operationcauses the white blobs of image 6 cancel out some of the lines of image4 that are the result of subsurface bubbles.

According to a fourth aspect of the present invention, a method ofdetermining the height of foam generated from a liquid in a tubecomprises subjecting a digital black and white image of the foam in thetube to the following electronic operations:

-   a) copying the digital image (image 1) into an electronic frame    (image 2) and then clearing image 2 from this frame to create a new    blank frame having the same pixel dimensions as the original digital    image 1;-   b) creating a rectangle in a graphics plane associated with the    electronic frame and merging the graphics plane with the image plane    of image 2 and specifying the rectangle is white or black and the    remainder is black or white, respectively, thereby creating a binary    image (image 3) of a rectangle on a contrasting background, the    rectangle having dimensions longer than the anticipated length of    the foam being measured and narrower than the width of the internal    dimension of the tube;-   c) subjecting the original digital image 1 to a segment process to    generate a binary image (image 4);-   d) subjecting image 3, after an inversion operation if required, and    image 4 to a Boolean “AND” operation to create an image (image 5)    representative of the foam height; and-   e) measuring image 5 to determine the foam height.

Preferably, in step b), the rectangle is white and the remainder isblack.

In the methods of the invention, it is preferred to use a gas diffusermeans to generate gas flow through the liquid to generate foamtherefrom. To obtain consistent results, it is necessary to “condition”the diffuser means by exposing it to the liquid under test for apredetermined period (as identified in step b) of the methods describedabove) before passing gas through the liquid. In many instances,exposure of the diffuser means to the liquid under test for thepredetermined period in steps b) of the methods is sufficient tocondition the diffuser means.

However, for some types of liquid, especially after the diffuser meanshas been allowed to stand dry for a period of time, it may be necessaryto iterate the steps of the methods for a number of times on the sameliquid until consistent results are obtained. When it is determined thatiteration of the method is required to condition the diffuser means inthis manner, the conditioning may be performed using a liquid that issimilar to the liquid under test. Once conditioned, it is only necessaryto clean the diffuser means between tests. Thus, once the diffuser meansis conditioned, a multiplicity of tests can be performed without theneed to re-condition the base by iteration of the methods, theconditioning of the diffuser means by the liquid under test that isachieved by steps b) of the methods being sufficient to enableconsistent results to be obtained.

The gas flow rates and predetermined periods are selected to ensure thefoam generated from any particular type of liquid under investigationdoes not completely fill the tube and overflow from it.

The methods of the invention also include the steps of cleaning thediffuser means and the tube between samples. The particular cleaningregime adopted may be dependent upon the liquids under investigation.Typically, however, such cleaning can be done after removal of thediffuser means from the liquid sample by placing the diffuser means intowater (preferably de-ionised water) and flowing gas through the diffusermeans; placing the diffuser means into a volatile liquid, for exampleacetone, and flowing gas through the diffuser means; and removing thediffuser means from the volatile liquid whilst continuing to flow gasthrough the diffuser means to evaporate the volatile liquid and dry thediffuser means. The cleaning process can be augmented with ultrasoniccleaning whilst the diffuser means is immersed in the water and thevolatile liquid.

Using the methods of the invention, a typical sample time includingsubsequent cleaning of the diffuser means is under 10 minutes. Owing tothe simplicity of the methods, a large number of samples can be testedusing them. The samples may be tested singly and sequentially or,alternatively, and more preferably, batches of samples can be tested inparallel. Accordingly, the methods of the invention include processingbatches of samples either sequentially or in parallel. When the samplesare processed in parallel, preferably more than 1 sample but not morethan 100 samples, more preferably at least 10 samples but not more than50 samples are processed together.

It would be possible to provide sufficient opto-electronic devices tomeasure the foams generated substantially simultaneously. However, it ispreferred to minimise the number of such devices used in the methods.Accordingly, it is preferred, in each batch of samples, to sequence theintroduction of the diffuser means into the liquid samples and theassociated gas flows and predetermined periods in successive tubes inthe batch such that for example a single optoelectronic device or asingle set of first and second opto-electronic devices, as the case may,is sequenced to each tube in the batch in turn to make the respectivemeasurements and capture the images as foam is generated in that tube.

According to a fifth aspect of the present invention, apparatus forassessing foam generation from a liquid comprising a tube open at oneend for receiving liquid samples and in which foams can be generated, agas diffuser means locatable within the tube and through which a gasflow through a sample located within the tube can be generated, a gasflow control means whereby gas flow through said diffuser means iscontrollable, an opto-electronic device located in use adjacent thetube, said opto-electronic device being capable of generating datarelating to foam in the tube, and control means for initiating action inresponse to input from the opto-electronic device.

The term tube as used herein means any conveniently shaped receptaclecapable of holding a relatively small sample of liquid, of receiving adiffuser and of containing foam generated from the liquid. As it needsto be optically transparent, it is made from glass or other opticallytransparent material that is effectively chemically inert to the liquidsunder test. Conveniently, the tube is a test tube typically having alength in the 150 mm, and has an internal diameter of 25 mm.

The gas diffuser means is conveniently a gas diffuser in the form of ametal sinter having a plurality of holes passing through it. The metalsinter is secured to one end of a tube that is connectable to a gassupply. The holes in the metal sinter may have a diameter in the range1-50 microns, more particularly in the range 2-20 microns, especially 2microns. Suitable sinters are available from Fisher Scientific, BishopMeadow Road, Loughborough, Leicestershire LE11 5RG. The gas supply tubetypically has a length of 500 mm and has an internal diameter of 5 mm.The gas supply tube is connected to the gas supply via a flexible, gasimpermeable tube.

A suitable flow controller controls gas flow through the diffuser means.Preferably, the controller is a mass flow controller, for example anOmega Mass Flow Controller available from Omega Engineering Ltd, 1 OmegaDrive, River Bend Technology Centre, Northbank, Irlam, Manchester M445Ex. The gas supply associated with the apparatus according to theinvention is typically a compressed air supply capable of supplying airat pressures up to 30 psi (2.07 bar).

According to one form of the fifth aspect of the present invention, theopto-electronic device is capable of detecting the top of foam beinggenerated in the tube and, in response thereto, providing an output tothe control means in response to which the control means is operable toterminate gas flow to the diffuser and to store the time taken frominitiation of the gas flow to termination of the gas flow.

According to another form of the fifth aspect of the present invention,the opto-electronic device is capable of detecting the top of foam beinggenerated in the tube and, in response thereto, providing an output tothe control means in response to which the control means is operable toterminate gas flow to the diffuser and to store that event, the controlmeans also being operable to control gas flow for a predetermined periodunless it receives input from the opto-electronic device within saidperiod and, if said period expires, terminating gas flow and initiatingrelative movement between the tube and the optoelectronic device wherebyparameters that enable the height of the foam generated in said periodare determinable.

Preferably, the opto-electronic device is moved relative to the tube.Preferably, the opto-electronic device detects the air/foam and thefoam/liquid interfaces, the difference between the positions of saidinterfaces being the height of the foam generated from the liquid insaid period.

In these forms of the fifth aspect of the present invention, theopto-electronic device is preferably a photoelectric device whose beamin use is interruptible by the foam but not by air or the liquid. Asuitable device is a turbidity detector available from ZymarkCorporation, Zymark Center, Hopkinton, Mass. 01748 USA.

According to yet another form of the fifth aspect of the presentinvention, the opto-electronic device is capable of capturing an imageof the foam from a location externally of the tube, the control meansbeing operable to initiate relative movement of the tube and theoptoelectronic device with respect to one another to position theopto-electronic device at a location relative to the tube at whichlocation, in use, the image is captured.

Preferably, apparatus according to the fifth aspect of the inventioncomprises a second opto-electronic device operable to generate data fromwhich the height of foam generated in the tube may be determined.

In one form of the apparatus according to the fifth aspect of theinvention, the tube and the second opto-electronic device are mountedfor relative movement with respect to one another. Preferably, the tubeis moved relative to the second opto-electronic device.

In one form of the apparatus according to the fifth aspect of theinvention, the second optoelectronic device detects the air/foam and thefoam/liquid interfaces and provides inputs into the control means fromwhich the height of the foam generated is determinable. In thisembodiment, the second opto-electronic device may be a photoelectricdevice as described previously.

In a preferred form of the apparatus according to the fifth aspect ofthe invention, the second opto-electronic device is fixed relative tothe tube position and is capable of capturing an image of the whole foamcolumn that, in use, is generated in the tube and transmitting such animage to the control means, the control means being operable to analysethe image so received to provide a measurement of foam height.

The opto-electronic devices capable of capturing images are convenientlycharged couple device (CCD) cameras, having an analogue or digitaloutput. As it merely needs to detect foam height, the second device isconveniently a low-resolution black and white camera, for example acamera having a pixel resolution of 752×582. For example, a Sony XC-75CEusing a Pentax 25 mm f1.4 lens is a suitable camera. The first device,as it is required to capture an image of the constituent bubbles of thefoam, is a medium- or high-resolution camera, for example a camerahaving a pixel resolution of 1300×1030. For example, an AxioCam MRCavailable from Carl Zeiss Vision GmbH is a suitable camera. Appropriatelens selection enables resolutions down to bubble sizes of 50 microns orless. A Computar 55 mm f2.8 Telecentric fens set at maximum zoom with a35 mm extension tube is preferred.

Although it is possible to consider using a single camera, ie a singleopto-electronic device, to capture images for both foam heightmeasurement and for image analysis, owing to the opposed requirements ofwide angle v narrow angle for each of the images, it is preferred to usetwo cameras, or two opto-electronic devices, as described above.

As will be well understood, suitable lighting has to be provided toenable the images to be captured. Conveniently, two light sources areused. To enable the second camera to capture an image of the whole foamcolumn, front lighting (relative to the camera position) but at anoffset position to avoid back reflection of the light to the camera isprovided during image capture. A suitable light source is a cold cathodeLP-100 lamp available from Universal Electronics Industries Ltd. For thefirst camera, the tube is lit from below to highlight the foam featuresand a suitable light source is a Schott cold light source with agooseneck fibre optic cable.

It is preferred that extraneous light sources are excluded to avoid backreflections that may affect the quality of the captured image.Preferably, a surrounding non-reflective environment is provided tominimise further the possibility of extraneous reflections beingcaptured as part of the images.

In preferred embodiments of the apparatus according to the fifth aspectof the invention, the apparatus further comprises a workstation at whichis located the opto-electronic device or devices and automated handlingequipment for moving the tube relative to said workstation and forpositioning the gas diffuser means in the tube, said control means beingadapted to control said automated handling equipment to move the tube toand from the workstation, to move the tube and the opto-electronicdevice or devices relative to one another and to move the gas diffusermeans into and out of the tube.

Preferably, one or more tubes in which cleaning fluids for the gasdiffuser means are locatable are provided at the workstation or at aseparate, cleaning, workstation, said automated handling equipment beingcontrollable by the control means to sequentially move the gas diffusermeans between the first tube and the cleaning tube or tubes. Anultrasonic cleaner is preferably provided at this location. The tubescontaining an appropriate cleaning fluid are located in an ultrasonicbath and are replaced after each cleaning cycle.

The present invention, in a sixth aspect, encompasses apparatus forassessing foam generation from a liquid comprising a workstation atwhich is located an opto-electronic device capable of generating datarelating to foam generated from liquid located in a tube, a gas diffusermeans locatable within a tube into which a liquid sample can be locatedand through which a gas flow into such a sample can be created, a gasflow control means whereby gas flow through said diffuser means iscontrollable, automated handling equipment for moving a tube relative tosaid workstation and for positioning the gas diffuser means in such atube, and control means for initiating action in response to input fromthe opto-electronic device and being adapted to control said automatedhandling equipment to move a tube to and from the workstation andrelative to the opto-electronic device whilst it is located at theworkstation and to move the gas diffuser means into and out of a tube.

Automated sample handling is achieved using a Zymark XP trackless robotsystem, available from Zymark Corporation, Zymark Center, Hopkinton,Mass. 01748 USA, with a variety of associated workstations. Control ofthe system and the opto electronic device is carried out by means ofEasylab robot control programming language.

As discussed in relation to the methods of the invention, althoughsample tubes may be fed sequentially through the foam-generation,measurement and cleaning cycle, samples may be processed in parallel.Thus, in another embodiment, the control means and the automatedhandling means are capable of moving the opto-electronic devicesrelative to the workstation passed a plurality of locations at whichsample tubes are locatable. In this embodiment, preferably a pluralityof diffuser means are provided each with it own cleaning station.

Associated with the or each workstation may be liquid supply means suchas liquid injectors to enable samples to be introduced to the sampletubes, to provide fresh cleaning fluids to the cleaning stations and toprovide automated waste disposal. Alternatively, racks of sample tubesmay be prepared remotely from the workstation and the racks can then beintroduced to a workstation accessible by the automated handling means.Following use, the sample tubes may then be disposed off, this beingmore economical than cleaning the sample tubes and re-using them. Thetubes for the cleaning station can be managed in a similar manner.

A particularly preferred form of apparatus for assessing foam generationfrom a liquid comprises at least one first workstation at which islocated, in use, sample tubes and cleaning tubes, a second workstationat which is located sample dispensing means, a third workstation atwhich, in use, cleaning tubes are locatable, a fourth workstation havinga parking location for receiving a gas diffuser means that can be placedwithin a sample and through which gas flow can be generated and a gasflow control means whereby gas flow through said diffuser means iscontrollable, and a fifth workstation at which is located anopto-electronic device capable of generating data relating to foamgenerated from liquid located in a sample tube, said apparatus furthercomprising automated handling equipment and control means for initiatingaction in response to input from the opto-electronic device and beingadapted to control said automated handling equipment, in use of theapparatus, to move cleaning tubes between the first and thirdworkstations and to move sample tubes from the first workstation to thefourth workstation, to locate the gas diffuser means in the sample tubeand to move the sample tube containing the gas diffuser means to thefifth workstation and to move the tube and the opto-electronic devicerelative to one another.

The invention also includes at least one library of data relating atleast to the foam properties of liquids, said data having been generatedusing the methods and/or apparatus according to the invention.

The invention will now be illustrated by reference to the drawing andfollowing examples. The drawings are:

FIG. 1 is a schematic plan view of automated sample handling andmeasuring apparatus according to the invention;

FIG. 2 is a graph of time to generate a specified height of foam vvolume of sample using Sample 3 as described in Example 1;

FIG. 3 is a graph of the results of foam heights achieved over timeusing Sample 3 as described in Example 1;

FIG. 4 is a graph of the results of foam heights achieved over timeusing a multiplicity of portions Sample 3 as described in Example 1 todemonstrate reproducibility;

FIG. 5 has two graphs relating to a first set of samples and it iscomparing foam height data obtained using an ASTM method (left handgraph) and time to specified height obtained using the invention (righthand graph) and as more particularly described in Example 1;

FIG. 6 has two graphs relating to a second set of samples and it iscomparing foam height data obtained using an ASTM method (left handgraph) and time to specified height obtained using the invention (righthand graph) and as more particularly described in Example 1;

FIG. 7 has two graphs relating to a first set of samples and it iscomparing foam height data obtained using an ASTM method (left handgraph) and foam height obtained using the invention (right hand graph)and as more particularly described in Example 1;

FIG. 8 has two graphs relating to a second set of samples and it iscomparing foam height data obtained using an ASTM method (left handgraph) and foam height obtained using the invention (right hand graph)and as more particularly described in Example 1;

FIG. 9 is a flow diagram of the sequences used to capture images of foamand to process them to obtain information relating to the foam asdescribed in Example 2.

FIG. 10 is a graph of the results of Samples 1 and 3 as described inExample 2 and in Table 9.

In FIG. 1, is shown an automatic sample handling and testing apparatusin accordance with the invention. The apparatus 10 has a Zymark XP robotsystem 12 in which the robot arm 14 is mounted both for rotation about avertical axis 16 and in the direction of said axis 16. One end of thearm 14 has a gripper mechanism 18 by which sample tubes 20 can begripped.

Rotation of the robot arm 14 about the axis 16 enables a plurality ofworkstations to be accessed. The number of workstations in the apparatus10 can be varied to suit the application. In FIG. 1, the apparatus 10 isshown as having the following workstations:

-   -   three tube holding stations 22 at which racks 24 of sample tubes        20 and cleaning tubes 36 are located;    -   a liquid dispensing station 26 at which are located a plurality        of liquid dispensers (not shown);    -   a gas diffuser parking station 28 having a gas diffuser 30 shown        in its parked location, and a location 32 at which a sample tube        20 can be positioned;    -   a gas diffuser cleaning station 34 at which are locatable        cleaning tubes 36 containing cleaning liquids, the tubes 36        being locatable in an ultrasonic bath 38;    -   a foam height measurement station 40 at which is located an        opto-electronic device 42 such as a photodiode turbidity        detector, available from Zymark Corporation, Zymark Center,        Hopkinton, Mass. 01748 USA, which is configured to allow the        robot arm 14 to pass the length of a sample tube 20 in front of        the detector as the arm 14 moves vertically long the axis 16 and        is capable of detecting air/foam and foam/liquid interfaces; and    -   an image capture and analysis station 44 at which are located        cameras 46 and 48 and a locator 50 for a sample tube 20.

The cameras 46, 48 were two CCD cameras that were capable of capturingimages of foam in the tubes. The camera 46 was an AxioCam MRC camerafitted with a Computar 55 mm f2.8 Telecentric lens set at maximum zoomwith a 35 mm extension tube. It is positioned with the front of its lens1500 mm from the location of the wall of a tube 20. Camera 48 was a SonyXC-75CE fitted with a Pentax 25 mm f1.4 lens located about 280 to 350 mmfrom the tube 20. Station 44 was surrounded by a non-reflective, lightneutral environment to prevent unwanted reflections being captured asparts of the images of the foams. Station 44 was also provided with acold cathode LP-100 lamp light source positioned above and in front ofthe tube position relative to the camera 48 so that the foam is lit fromthe front and at an angle thereto to minimise stray reflections; and aSchott cold light source with a gooseneck fibre optic cable the end ofwhich was located immediately beneath the tube position so that the foamis lit from below when camera 46 was used.

In practise, it is likely only one of the stations 40 and 44 will bepresent but, for convenience, both are shown. The operation of thestations 40 and 44 is described below in Examples 1 and 2, respectively.

The gas diffuser 30 consists of a metal sinter (10 mm long×10 mmdiameter and having 2 micron diameter holes (available from FisherScientific, Bishop Meadow Road, Loughborough, Leicestershire LE11 5RG)attached to a length of glass tube 125 mm long×5 mm inside diameter. Theglass tube was in turn attached through a flexible air-impervious tubeto an Omega Mass Flow Controller having a gas flow range (1-10) ml/min.

In general, the operation of the apparatus 10 is as follows.

A plurality of sample tubes 20 is located in one or more racks at thestations 22 and constituent components of sample liquids to be testedare placed in the liquid dispensers at station 26. Cleaning tubes 36containing cleaning liquids are located in one rack at one of thestations 22.

The robot arm 14 is rotated about the axis 16 between the stations 22and 34 to transfer cleaning tubes 36 to station 34. The robot arm 14 isthen rotated between the stations 22 and 26 to transfer a sample tube 20to the station 26 where constituent components of the sample liquids tobe tested are added to the sample tube 20 in variably controlledamounts. The robot arm 14 is rotated about the axis 16 to present thesample tube 20 containing the sample to be tested to stations 28 andeither 40 or 44 as is described in more detail below in Examples 1 and2.

Once the sample has been tested, the robot arm 14 returns the sampletube 20 to its location in its rack 22 at the relevant station 22 andthen collects the used cleaning tubes 36 and returns them to their rack24 at the relevant station 22.

The sequence is then repeated, the composition of the samples generatedat station 26 to be tested each of differing in its composition to theother samples. The differences between samples may be relatively largewhen scoping experiments are being performed or may be relatively smallwhen optimisation experiments are being performed.

Reference is now made to the Examples.

EXAMPLE 1

A number of foam assessments were carried out (using the materialsidentified in Table 1 made up into samples as shown in Table 2).

At one of or more of the stations 22 were located sample receiving glasstest tubes 20 (each 125 mm long×25 mm diameter). Samples (15 ml) to betested were introduced into the tubes 20 from the dispensers at station26 as described above with reference to FIG. 1. With a sample tube 20 atstation 28, the robot 12 introduced into the tube 20 the gas diffuser 30and then moved the tube 20 with the gas diffuser 30 in it to station 40at which foam was generated and measured as is described in more detailbelow.

TABLE 1 Materials tested Material No Material Description M1 Emkarate* Apolyol ester refrigerant lubricant available RL 22H from Uniqema.Lubricant M2 Lubricant A methyl end capped polypropylene glycol. M3Zerol 150 An alkylbenzene available from the Chevron Company. M4 Tego793 An antifoaming agent available from Thomas Goldschmidt. M5 RC8301 Anantifoaming agent available from Rhein Chemie. M6 Silicone Fluid 50 Afoam promoting agent available from Akrochem. M7 Fluorolink D10 Apolydimethyl siloxane foam promoting agent available from Ausimont.*Trade mark of the ICI Group of companies.

Following foam generation and measurement, the gas diffuser 30 wasremoved from the tube 20 and was moved to station 34 at which it wascleaned by being placed in a cleaning tube 36 containing water and airwas caused to flow through the diffuser 30, the diffuser 30 then beingplaced in a cleaning tube 36 containing acetone with the air flow beingmaintained and then being removed from the acetone and left in air withthe air flow being maintained to dry the diffuser 30. During thecleaning phase, the ultrasonic bath 38 was operated. The gas diffuser 30was then returned to the parking station 28; the sample tube 20 wascollected from station 40 and returned to its location in the rack atone of the stations 22; and the cleaning tube 36 containing, water wasreturned to its rack 24 at the relevant station 22 to be replaced by afresh tube 36 containing water. In this particular Example, the diffuser30 is primarily cleaned by the water; the acetone is used primarily as adrying aid. Consequently, it was not necessary to change the cleaningtube 36 containing the acetone between individual tests.

TABLE 2 Samples of Lubricant Compositions Material No M1 M2 M3 M4 M5 M6M7 2Sample No Wt % Wt % Wt % Wt % Wt % Wt % Wt %  1 100  2 50 50  3 5050  4 49.99 49.99 0.02 ppm ppm ppm ppm  5 50 50 20  6 50 50 50  7 50 50200  8 50 50 20  9 50 50 50 10 50 50 200 11 50 50 20 12 50 50 50 13 5050 200 14 50 50 20 15 50 50 50 16 50 50 200 17 50 50 20 18 50 50 50 1950 50 200 20 50 50 20 21 50 50 50 22 50 50 200 23 50 50 20 24 50 50 5025 50 50 200 26 50 50 20 27 50 50 50 28 50 50 200

The specific routine adopted in testing the samples at station 40 was:

-   -   1) locate the diffuser 30 in a tube 20 containing the sample for        30 seconds without any airflow during which period the tube 20        is moved to station 40;    -   2) introduce gas into the sample through the diffuser 30 at a        rate of 4 ml/min for 5 minutes unless the foam triggers the        optical detector 42 which in turn causes the gas flow to stop        and records the time at which the flow is stopped;    -   3) if, after 5 minutes, the optical detector 42 has not been        triggered, stopping the gas flow and causing relative movement        between the tube 20 and the detector 42 to enable the detector        42 to determine the relative positions of the air/foam and        foam/liquid interfaces to enable the height of the foam to be        determined.    -   4) removing the diffuser 30 from the sample, moving it to        station 34 and placing it in a cleaning tube 36 containing water        and flowing air through the diffuser for 3 minutes;    -   5) removing the diffuser 30 from the water and placing it in a        cleaning tube 36 containing acetone and flowing air through the        diffuser 30 for 0.5 minutes; and    -   6) removing the diffuser 30 from the acetone and leaving it in        air and flowing air through it for 1.5 minutes to dry it.

At this stage, the diffuser is returned to the parking station 28 and isthen ready for location in a subsequent sample.

In Table 2, Sample 1 essentially does not foam, Sample 2 is a lowfoaming composition, Sample 3 is a medium foaming composition and Sample4 is a high foaming composition.

Sample 3 was used to determine a suitable sample volume to use. This wasdone by testing portions of different volumes and determining the timetaken for the foam to reach the detector 42, which was set at 55 mmabove the liquid/air interface. This was done twice. The results aregiven in Table 3 and are plotted as a graph in FIG. 2. As can be seenfrom FIG. 2, 15 ml is a suitable sample volume to use to achieve maximumfoam height in a reasonable time.

Sample 3 was used to determine a suitable foaming times. This was usingthe above procedure except the foam height was measured at intervalswhilst the gas flow was maintained in the sample. The results are shownin Table 4 and are plotted on a graph in FIG. 3. As can be seen fromFIG. 3, the foam height reaches a plateau after about 50-55 seconds andreaches a height of about 8 cm, ie well within the confines of the tube.

TABLE 3 Average Time Volume (ml) Time (seconds) Time (seconds) (Seconds)First Run 10 147.6 153.78 150.69 11 61.62 64.82 63.22 12 58.2 56.0257.11 13 53.84 53.28 53.56 14 52.38 49.56 50.97 15 47.96 46.70 47.33Second Run 10 177.84 191.02 184.43 11 57.74 58.02 57.88 12 53.28 53.5053.39 13 51.26 51.78 51.52 14 50.34 48.30 49.32 15 46.74 46.70 46.72

Sample 3 was then used to determine the reproducibility of thetechnique. This was done by repeatedly testing Sample 3 using a seriesof tubes 20. The tests were run both forward and reverse in respect ofthe tube sequence. The weight of the tubes 20 both empty and containingthe 15 ml portions of Sample 3 was also recorded. The results of thosetests are detailed in Table 5 and are plotted in a graph in FIG. 4. Ascan be seen from FIG. 3, the test is reproducible within acceptablelimits across a series of tubes 20 and is not dependant on sequencedirection or on minor variations in tube/sample weight.

Samples using different levels of additives were then tested asdescribed above in this Example. The same Samples were also tested usingASTM D892-95. The results were compared as described below.

To enable a comparison to be made between the ASTM method and the methodaccording to the invention, the results were normalised by setting theresults for the Samples containing no additives, ie Samples 2 and 3, asunity (1) and calculating the results of the other Samples as a ratio ofthe result in question to the result of those Samples 2 and 3. Theresults obtained are given in Table 6 and are plotted in FIGS. 5 to 8,the ASTM method results being shown in the left hand graph in each ofthe FIGS. 5 to 8 and the results from the invention being shown in theright hand graph in each of the FIGS. 5 to 8.

TABLE 4 Run 1 Run 2 Run 3 Time Height Time Height Time Height (seconds)(cm) (seconds) (cm) (seconds) (cm) 30.12 5 30.1 4.2 30.1 4.3 31.04 4.531 4.8 31.02 4.8 32.12 4.9 32.08 4.8 32.08 5.1 33.04 5.1 33 5.1 33 5.434.1 5.4 34.06 5.3 34.06 5.4 35.02 5.6 35.12 5.4 35.12 5.7 36.08 5.736.04 5.6 36.04 5.8 37.14 6.0 37.1 5.9 37.1 6.1 38.06 6.0 38 6.0 38.026.2 39.12 6.2 39.08 6.2 39.08 6.3 40.04 6.5 40.14 6.4 40.14 6.6 41.1 6.741.06 6.7 41.04 6.9 42.02 6.9 42.12 6.8 42.12 7 43.08 7.1 43.02 7.243.02 7.3 44 7.3 44.08 7.4 44.1 7.3 45.06 7.4 45 7.5 45 7.6 46.12 7.646.06 7.6 46.06 7.7 47.04 7.8 47.14 7.8 47.12 7.8 48.1 7.8 48.04 7.848.04 7.8 49 7.8 49.1 7.9 49.1 7.9 50.08 7.9 50.02 7.9 50.02 7.9 51 7.951.08 7.9 51.08 8 52.06 8 52 8 52 8 53.12 8 53.06 8 53.06 8 54.04 854.12 8.1 54.12 8.1 55.1 8 55.04 8.1 55.04 8.1 56.02 8.1 56.1 8.1 56.18.2 57.08 8.1 57.02 8.3 57 8.2 58 8.1 58.06 8.3 58.08 9.2 59.08 8.259.14 9.3 59.14 9.2

The data produced in FIGS. 5 and 6 show comparative data between thestandard ASTM method and the automated method according to the inventionby employing ranking as a function of time taken to produce foam. Ashigher foaming Samples reach the fixed height in a shorter time ascompared to lower foaming Samples, to compare the results with the ASTMfoam heights, the results of Samples 2 and 3 were divided by the resultsof the other Samples to produce the normalised figures.

TABLE 5 Tube Tube Order Tube Order Number −1 −29 −29 −1  1 47.20 46.34 2 45.78 44.88  3 45.78 44.16  4 45.74 44.90  5 46.48 44.92  6 47.9047.06  7 45.04 44.92  8 45.04 44.90  9 44.32 44.18 10 46.48 47.06 1144.30 44.92 12 46.50 46.34 13 45.76 47.06 14 43.60 45.64 15 44.32 44.9016 45.04 45.64 17 44.32 47.08 18 44.24 45.62 19 44.30 44.90 20 44.3044.88 21 44.22 44.92 22 43.58 44.90 23 43.58 44.90 24 44.34 44.92 2543.58 45.62 26 43.58 46.36 27 42.88 44.18 28 43.60 44.18 29 43.58 47.06Average 44.85 45.37 SD 1.26 0.93 RSD 2.80 2.04

The ranking compared to the ASTM method is the same but the resolutionbetween samples in not as pronounced. However the time taken to producethe data in accordance with the invention is more rapid than the ASTMmethod.

Data produced employing the second method of detection, measuring theheight of foam produced, shows good comparability to the data producedusing the ASTM method on the same sample set. (FIGS. 6 and 7) In thisinstance, the results for the Samples were divided by the results forSamples 2 and 3 to produce the normalised figures.

The use of a combination of these testing methods allows evaluation ofsamples with widely differing foaming capabilities without danger ofloss of sample containment for high foaming samples without the need tovary the gas flow.

TABLE 6 Time to Sample fixed foam Height of ASTM Foam No height (s)Normalised Foam Normalised Height (mm) Normalised 3 57.4 1.00 2.7 1.0280 1.00 5 51.1 1.12 5.0 1.8 420 1.50 6 49.9 1.15 5.5 2.0 640 2.29 750.2 1.14 6.1 2.2 630 2.25 3 57.8 1.00 3.2 1.0 280 1.00 8 52.2 1.11 3.81.2 160 0.57 9 50.8 1.14 4.3 1.4 310 1.11 10 51.8 1.12 4.7 1.5 320 1.143 52.7 1.00 3.3 1.0 280 1.00 11 58.3 0.90 4.6 1.4 350 1.25 12 55.1 0.964.7 1.4 375 1.34 13 57.3 0.92 4.7 1.4 125 0.45 3 52.6 1.00 3.3 1.0 2801.00 14 50.2 1.05 5.4 1.6 304 1.09 15 50.2 1.05 5.5 1.6 375 1.34 16 49.51.06 6.1 1.8 450 1.61 2 172.7 1.00 0.4 1.0 30 1.00 17 55.1 3.13 1.6 4.185 2.83 18 41.6 4.15 3.7 9.3 300 10.00 19 39.4 4.39 5.5 13.6 500 16.67 257.4 1.00 0.7 1.0 30 1.00 20 51.1 1.12 0.6 1.0 30 1.00 21 49.9 1.15 0.50.8 20 0.67 22 50.2 1.14 0.6 0.9 25 0.83 2 300.0 1.00 0.6 1.0 30 1.00 2348.0 6.25 5.0 8.2 410 13.67 24 49.9 6.01 4.9 8.2 435 14.50 25 53.1 5.654.6 7.6 320 10.67 2 146.5 1.00 0.7 1.0 30 1.00 26 57.7 2.54 2.7 3.9 903.00 27 47.6 3.08 3.5 4.9 125 4.17 28 47.1 3.11 4.6 6.5 350 11.67

EXAMPLE 2

Solutions of shampoos were analysed and compared as follows:

At one of or more of the stations 22 were located sample receiving glasstest tubes 20 (each 125 mm long×25 mm diameter). Samples (15 ml) to betested were introduced into the tubes 20 from the dispensers at station26 as described above with reference to FIG. 1. With a sample tube 20 atstation 28, the robot 12 introduced into the tube 20 the gas diffuser 30and then moved the tube 20 with the gas diffuser 30 in it to station 40at which foam was generated and measured as is described in more detailbelow.

Following foam generation and image capture, the gas diffuser 30 wasremoved from the tube 20 and was moved to station 34 at which it wascleaned by being placed in a cleaning tube 36 containing water and airwas caused to flow through the diffuser, the diffuser 30 then beingplaced in a cleaning tube 36 containing acetone with the air flow beingmaintained and then being removed from the acetone and left in air withthe air flow being maintained to dry the diffuser 30. During thecleaning phase, the ultrasonic bath 38 was operated. The gas diffuser 30was then returned to the parking station 28 and the sample tube 20 wascollected from station 44 and returned to its location in the rack atone of the stations 22. In this particular Example, the diffuser 30 isprimarily cleaned by the water; the acetone is used primarily as adrying aid. Consequently, it was not necessary to change the cleaningtube 36 containing the acetone between individual tests.

The test samples were 0.1% by weight of shampoo in deionised water. Foamheights of 3 to 6 cm were generated depending upon the foaming abilityof the formulation.

The samples selected were:

Sample 1—Pantene Pro-V shampoo available from The Proctor & GambelCompany

Sample 2—Euro Gold shampoo available from Johnson & Johnson

Sample 3—a development shampoo.

The specific routine adopted in testing the samples was:

-   -   1) locate the diffuser 30 in a tube 20 containing the sample for        30 seconds without any airflow during which period the tube 20        is moved to station 44;    -   2) introduce gas into the sample through the diffuser 30 at a        rate of 4 ml/min for 4 minutes;    -   3) stop the gas flow and capture a first image using the camera        48;    -   4) analysing the image to generate a foam height measurement and        adjusting the relative positions of the tube and the camera 46        such that the camera 46 is located opposite the tube at a        position that is halfway between the air/foam and foam/liquid        interfaces and capturing a second image of the foam using the        camera 46;    -   5) removing the diffuser 30 from the sample, moving it to        station 34 and placing it in a cleaning tube 36 containing water        and flowing air through the diffuser for 2 minutes;    -   6) removing the diffuser 30 from the water and placing it in a        cleaning tube 36 containing acetone and flowing air through the        diffuser for 0.5 minutes; and    -   7) removing the diffuser 30 from the acetone and leaving it in        air and flowing air through it for 1.5 minutes to dry it.

At this stage, the diffuser 30 is returned to the parking station 28 andis then ready for location in a subsequent sample.

Previous work had established that analysis of bubbles at the water/foamhead interface did not lead to strong differentiation of theformulations whereas analysing the bubbles from half way up the foamhead gives better differentiation, ie the foam is “aged” as compared tofoam at the water/foam head interface. The images were analysed asdescribed in more detail below.

Similarly as described with reference to Example 1, the conditions(time, flow rates etc) used to generate the foams from the samples weredetermined before assessing the shampoo samples.

In assessing shampoo samples, it was found that it was necessary priorto running a series of samples to condition the diffuser 30. This isparticularly critical if the diffuser 30 has not been used for sometime. The conditioning was done conveniently using sodium lauryl ethersulphate (SLES). To condition the diffuser 30, steps 1 to 7 describedabove were iterated using a number of samples of SLES until the foamheights and the analysed bubble size distribution of the foams wereconsistent. Once consistency of results had been achieved, actualsamples to be tested were then run.

It will be appreciated that, if the samples to be tested containingredients significantly different from SLES, then another suitableliquid should be selected to condition the gas diffuser 30.

Analysis of the images was performed using a combination of imageprocessing followed by image analysis. In both cases, a Zeiss KS300image analyser was employed. The final step of the process is theconversion of the processed image to a binary image where all features(bubbles) are white and the separating bubble walls are black. Imageanalysis was then a process of measuring parameters associated with theindividual white regions in the binary image.

In particular, the image capturing and subsequent processing/analysiswas done as follows:

Image Capture

-   1. Capture image* of whole foam head using the camera 48 and save    this image in a designated file and processing and analysing the    captured image to provide a measurement for the foam height;-   2. switch between cameras 48 and 46 so that the live image comes    from the camera 46;-   3. turn off the cold cathode LP-100 lamp light source associated    with the camera 48 and turn on the Schott cold light source for the    camera 46;-   4. move the camera 46 and the tube 20 relative to one another to    locate the camera 46 at a position opposite the tube 20 that is half    the foam height, ie midway between the air/foam and foam/liquid    interfaces; and-   5. capture an image of bubbles at the glass tube surface using the    camera 46 and saving this image in a designated file and processing    and analysing the captured image to provide parameters of interest.    *The output from the camera 46 is analogue. The output from the    camera 46 is converted into a digital image in a ‘framegrabber’    board of the computer running the software. It is this digital image    that is processed and analysed.    Foam Height Analysis-   1. copy the digital image (image 1) generated by the framegrabber    board from the output from camera 48 into an electronic frame (image    2) and then clear the frame to create a blank image (new image 2)    having the same pixel dimensions as the original digital image    (image 1);-   2. create a rectangle in a graphics plane associated with the    electronic frame and merge the graphics plane with the image plane    of image 2. Specify the rectangle is white and the remainder is    black thereby creating a binary image (image 2) of a white    rectangle, the rectangle having dimensions longer than the    anticipated length of the foam being measured and narrower than the    width of the internal dimension of the tube and clear the graphics    plane of the frame. It is important that the rectangle passes down    the central axis of the foam head seen in image 1 but is not as wide    as the head;-   3. subject the original digital image 1 to a SEGEMENT process to    generate a binary image (image 3) and:    -   3.1 perform a FILL operation to fill in holes or other defects        in the white object (the foam) of image 3;    -   3.2 perform an OPEN operation on image 3 to remove the fine        structure at the edge of the white object; and    -   3.3 perform a DILATE operation on the white object so that it is        the same size as the original foam head;-   4. subject new image 2 and image 3 to a Boolean “AND” operation to    create an image (image 4) representative of the foam height;-   5. measure image 4 to determine the foam height. The height is    determined by measuring the area and, knowing the width, calculating    a mean height measurement over the central part of the foam head;    and-   6. provide a signal to control the position of the camera 46 and    store the height information.

During the above routine, the software loads the calibration file forcamera 48 at this magnification so that distances are correct. Thiscalibration step is performed separately through the capture of an imageof a standard scale placed in the exact position usually occupied by theglass tube 20.

Foam Bubble Size Measurement

-   1. Select one information channel, eg red, of the digital image from    camera 46 and create therefrom a black and white image (image 1) in    an electronic frame;    -   1.1. subject image 1 to a smoothing operation using a lowpass        filter to create a smoothed image (image 1 a);    -   1.2. subject image 1 to a shade correction process using image 1        a to produce an image (image 1 b) corrected for shading        differences.-   2. subject image 1 b to a WATERSHED SEGMENTATION process to produce    an image (image 2) in a graphics plane associated with the    electronic frame, image 2 being a line representation of bubble    walls of the foam;-   3. clearing image 1 from the image plane of the frame and merging    the graphics plane with the image plane of the frame to create an    image (image 3) consisting of white lines representing the bubble    walls and a black background and clearing image 2 from the graphics    plane;-   4. inverting image 3 to create an image (image 4) in which the    bubbles are white and the bubble walls are now black;    -   4.1. on image 4 perform an ERODE operation to remove a line of        white pixels from the outside of the white blobs so that the        separation between them is greater (image 4 a);    -   4.2. on image 4 a perform an OPEN operation which removes sharp        edges from the white blobs but retains the basic size of the        objects and place that image in the same frame as image 4 a to        replace image 4 a (image 4 b);-   5. subject image 1 b to a straight ADAPTIVE SEGMENTATION to produce    a binary image (the adaptive segmentation is done “locally” in the    image not globally) (image 5). The purpose of this step is    specifically to produce an binary image of the big bubbles alone to    enable features arising from bubbles behind, in the image, the big    bubbles to be minimised. This is achieved by setting the size    parameter and the threshold parameter (the big bubbles tend to also    be lighter) for the adaptive segmentation process before carrying it    out. Image 5 essentially contains images of just the big bubbles (or    the main parts of them). Image 5 is then subjected to a SCRAP    operation to remove small white features and a FILL operation to    fill in holes in the white objects so they are more complete to    generate an image 6;-   6. invert image 4 b so that is shows white lines and black blobs    (image 4 c). Some of these white lines are incorrect since they are    from subsurface bubbles;-   7. subject the image 4 c and image 6 to a Boolean “SUBTRACT”    operation to generate an image 4 d. The Boolean operation causes the    white blobs of image 6 cancel out some of the white lines of image 4    c and those are the lines produced owing to the presence of the    subsurface bubbles. Image 4 d is then subjected to the following    operations in sequence;    -   7.1. a THIN operation that reduces the width of the lines and a        PRUNE operation so that the image 4 d is now of white lines with        no white line “tails” surrounding black blobs;    -   7.2. an INVERT operation so that the image 4 d is of black lines        surrounding white blobs;    -   7.3. an ERODE operation to obtain better separation between the        white blobs;    -   7.4. an OPEN operation (ie an ERODE operation followed by a        DILATE operation—it tends to erode off sharp edges but leaves        the basic size and shape of the object unchanged) giving the        finished image 4 d; and-   8. measure the dimensions of the white blobs in image 4 d and put    the data in a database. A calibration carried out at the start of    the run is then used for all measured images. This is performed as    described earlier by capturing an image of a standard scale placed    in the exact position of the tube.

The above-described sequences are set out in FIG. 9 as a flow chart.

It will be appreciated the various electronic operations used to processthe images captured by the cameras as described herein, for examplewatershed and adaptive segmentations, invert, thin, open, erode, dilateetc, are well understood in the art. Information relating to such termsis generally available and, in particular, reference is made to“Computer-assisted microscopy: the measurement and analysis of images”,John C. Russ, Plenum Press, New York (1990) and “The Image ProcessingHandbook” 2nd Edition, John C. Russ, CRC Press, Boca Raton (1995).

The bubble parameters measured were: Area and DCircle (area of thecircle with the same area as the object). Data output was done in twoways:

-   -   a histogram of counts per DCircle size range (e.g. within        100-150 microns, 150-200)    -   sum of the areas of the bubbles in each such size range (area is        related stereologically to volume)

Important parameters defining the bubble size distribution are seen tobe:

-   -   1. The range in size between the biggest and smallest bubble.    -   2. Mean Dcircle.    -   3. Median DCircle (deviates from the mean if the distribution is        skew).    -   4. Standard deviation in bubble sizes.    -   5. The amount of skew of the distribution i.e. is the        distribution symmetrical or does it have, say, a tail to the        high bubble diameter side.

Characteristic images of bubbles were obtained for Samples 1 to 3. Highfoaming formulations tended to give small bubbles with a narrow sizedistribution. A summary of the data measured for the Samples is given inTable 7.

TABLE 7 Stan- Median Mean dard Size range diameter diameter Devi- Skew-Foam Counts (microns) (microns) (microns) ation ness Sample 1 111362-298 136.2 138.8 38.5 0.5 Sample 2 1433 15-380 125.8 131.8 36.6 1.5Sample 3 1630 15-514 135 147.7 57.8 1.9

The above data relates to the analysis of just one image from oneformulation, though in practice many runs are performed and the data isaveraged. It is clear from the above that Sample 3 contains the largestbubbles since the range of bubble diameters is high as is the meanbubble diameter.

Other methods of displaying the data are given below.

For example, the number of bubbles within a certain diameter range maybe counted. In Table 8, the skew in the Sample 3 distribution is clearto see since there are a number of counts in the large Dcircle sizerange.

TABLE 8 DCIRCLE size range Counts Counts Counts (microns) Sample 1Sample 2 Sample 3 0 50 0 2 7 50 100 187 221 213 100 150 540 864 870 150200 298 280 322 200 250 83 52 119 250 300 5 10 44 300 350 0 2 33 350 4000 2 17 400 450 0 0 2 450 500 0 0 2 500 550 0 0 1 550 600 0 0 0

Another method of displaying the data is given by summing of the areasof the bubbles in each size range (e.g. 100-150 microns etc), see Table9. This method accentuates the skew in the distribution of Sample 3, thesum of the areas giving a good approximation of the volume distributionof bubbles that exists in the foam. The areas for Samples 1 and 3 areplotted in FIG. 10

TABLE 9 The Sum of the Areas of Bubbles in each Diameter Range MaxBubble Diameter (microns) Sample 1 Sample 3 50 0.00 0.00 100 1.29 1.10150 10.89 6.92 200 7.46 6.77 250 4.64 3.04 300 2.56 0.29 350 2.70 0.00400 1.81 0.00 450 0.29 0.00 500 0.35 0.00 550 0.21 0.00 600 0.00 0.00

Sum of the areas is in millions of sq microns

1. A method of assessing foam generated from a liquid comprising: a)introducing a measured quantity of the liquid into at least one tube; b)passing a gas of a predetermined flow rate through the liquid togenerate foam; c) sensing the presence of foam using an opto-electronicthat is positioned proximate the exterior of the at least one tube; andd) controlling the flow rate of said passing gas based on a signal fromeither said sensor or a timer or both.
 2. The method of claim 1, whereinthe signal is generated upon the sensor detecting the presence of foam.3. The method of claim 1, wherein the signal is generated from the timerthat is set for a predetermined period of time.
 4. The method of claim1, wherein controlling the flow rate of said passing gas includesstopping said flow rate.
 5. The method of claim 1, wherein the sensordetecting the presence of the foam generated is proximate the air/foaminterface.
 6. The method of claim 1, further comprising adjusting theposition of either the tube or the sensor, or both, relative to eachother, to enable the sensor to sense the presence of foam.
 7. The methodof claim 6, wherein the adjusted position of the sensor enablesdetection of the foam proximate either the air/foam or foam/liquidinterface.
 8. The method of claim 6, wherein the position of the tube isadjusted.
 9. The method of claim 6, wherein the position of the sensoris adjusted.
 10. The method of claim 1, wherein the sensor is aphotodiode turbidity detector capable of sensing the presence of foamproximate the air/foam interface.
 11. The method of claim 1, wherein thesensor is a photodiode turbidity detector capable of sensing thepresence of foam proximate the foam/liquid interface.
 12. The method ofclaim 1, further comprising: a) capturing an image of the foam with atleast one camera; and b) analyzing the captured image for foam qualityparameters.
 13. The method of claim 12, wherein the at least one camerais a COD camera.
 14. The method of claim 1, wherein the at least onetube is two but not more than 100 tubes.
 15. The method of claim 1,wherein the method is assessing foam generated from a plurality ofliquids, comprising more than 1 but not more than 100 liquids.
 16. Themethod of claim 15, wherein the plurality of liquids are assessed inparallel.
 17. The method of claim 16, wherein the plurality of liquidsare assessed using a high-throughput screening apparatus comprising aplurality of workstations and a robotic arm having access to theworkstations.
 18. The method of claim 17, wherein the plurality ofworkstations comprises: i) a first workstation, wherein one or moreracks of tubes are located and cleaned; ii) a second workstation,wherein a liquid dispensing means is located, comprising a plurality ofliquid dispensors; iii) a third workstation, wherein cleaning tubes arelocatable; iv) a fourth workstation, having a parking location forreceiving a gas diffuser means can be placed within a liquid such thatgas can be passed through the liquid to generate foam, and having ameans to control the flow of gas passed through the liquid, and v) afifth workstation, having more than one sensor capable of sensing foamgenerated from a liquid located in the tube.
 19. The method of claim 15,wherein the plurality of liquids are assessed sequentially.